Essential oils are generally high
value, low volume commodities. This makes them attractive crops
to grow and process for smallholder farmers and remote
communities in the LDCs, where transport problems prevent them
from marketing high volume cash crops.

Fourteen monographs on essential
oil crops which are capable of yielding an income in a relatively
short space of time have been prepared. The oils featured in the
monographs have been selected for one of two reasons: i. there is
an existing commercial market for the oil with room for new
producers to enter, e.g. patchouli oil. ii. the oil contains a
major ingredient for which shortages may occur in the future,
e.g. safrole from sassafras oil.

The essential oil from a
particular species of plant may vary depending on where it has
been grown and how it has been processed. New producers should be
prepared to meet with some resistance when attempting to market
oils from new sources. They may be offered lower prices than
expected and, initially, sales may be slow. In order to be
successful a new supplier must satisfy buyers that his oil(s)
will meet the following requirements. i. uniform good quality ii.
stable price iii. continuity of supply

Building up buyer confidence
will, of necessity, take some time and new producers of essential
oils are encouraged to take this into account when beginning to
distil commercially essential oils.

Essential oils are aromatic
materials of vegetable origin, which are used in perfumery and
flavourings. They represent the "essential aroma" of
the plant from which they are obtained. The majority of essential
oils are produced by the process of steam distillation.

The essential oil of a plant
consists of many compounds which generally boil between 150°
300° C. If attempts are made to remove these compounds by dry
distillation many will decompose and the oil will be ruined.
However, the compounds are steam volatile and can be distilled
out of the vegetal materials at around 100° C.

When plant materials are steam
distilled chemical changes inevitably occur and the oil obtained
will not have an identical aroma to that of the original plant
material.

Preparation of material for
distillation varies with the material to be distilled. Some
material must be distilled immediately after harvesting, whereas
others can be (and are best) stored for a day or two before
distilling and finally there are materials which can be stored
indefinitely before distillation. In general, flowers should be
distilled immediately, whereas herbaceous material often benefits
from wilting for one or two days before distillation. Woody
materials may need to be ground and/or soaked before
distillation.

The preparation of the raw
material, the packing of the still and the rate/type of
distillation can be determined for a particular essential oil
crop from the literature or from experimental trials.

i. "Hydrodistillation"
- in this method the charge (which is usually comminuted) is
immersed totally in water which is boiled. The stills are of the
simplest type (see Figure 1: Simple still hydrpdistillation) and are used extensively by smallholder
producers of essential oils. Often they are heated over an open
fire. The disadvantages are that the heat is difficult to control
and hence the rate of distillation is variable. Also the
possibility exists for local overheating and "burning"
of the charge which can lead to a poorer quality oil. Improved
distillation control can be obtained by using steam from a
separate boiler, which is passed into a jacket around the still
or through a closed coil in the bottom of the still, to heat the
contents of the still. A further disadvantage of this system is
that it requires the heating of a large quantity of water adding
to costs and time needed for each distillation. However, it is
necessary for certain flower distillations e.g. rose and ylang.
It is also necessary for the efficient distillation of certain
woody materials e.g. sandalwood and cinnamon bark.

ii. Water/steam distillation this
is an improved method, the still contains a grid which keeps the
plant material above the water level (Fig. 2.
Water/Steam still) The
water is boiled below the charge and "wet" steam passes
through the plant material. Consequently, if an open fire is used
the plant material is protected from direct heat. In Fig. 2 the
still is heated by a steam jacket. It is important in both
water/steam and steam distillation that the still is packed
evenly and not too tightly so that steam can extract from the
complete charge efficiently. Over packing of the still can cause
the steam to force "rat holes" through the charge and
leave other parts of the charge unextracted.

iii. Steam Distillation - the
most advanced type of distillation is by direct steam provided
from a separate boiler. The still contains a grid plate under
which an open steam pipe is fitted (see Fig. 3. Steam
distillation unit).

The advantages of this type of
"dry" steam distillation are that it is relatively
rapid, therefore charging and emptying the still is much faster
and energy consumption is lower. The rapid distillation is also
less likely to damage those oils which contain reactive
compounds, e.g. esters

As a general rule all stills
should be insulated ("lagged") to reduce heat losses.
Their design and losses . Their design and construction should
also facilitate loading and unloading.

Condensers and Separators

The steam containing essential
oil vapour leaves the still and passes into a condenser by way of
a "gooseneck" (Fig. 4. Btillhead/Gooseneck). Some sort of gauze or screen is often
fitted at the mouth of the gooseneck to prevent plant material
being blown over into the condenser.

In the condenser the vapours are
cooled and condense. The simple form of condenser is shown in
Fig. 5. (see Fig. 5. Coil condenser). The vapours pass through a coiled tube
contained in a water bath and condensate is obtained at the
bottom of the condenser tube. It is important that condensation
is complete or oil may be lost by evaporation.

A more efficient type of
condenser is the multi-tubular type shown in Fig. 6 (see Fig. 6.
Multi-tubular condenser)
in which a series of parallel tubes are mounted inside a
cylindrical jacket through which cooling water is passed. This
design provides a large surface area for cooling in relation to
its volume.

The mixture of water and
essential oil leaves the condenser and flows into a separator,
called a florentine flask, in which they separate into two
layers.

The essential oil will generally
be lighter than water, the oil floats to the surface and the
distillate water drains away.

It is important that the oil
separators should be large enough in volume to minimize
turbulence because significant amounts of oil can be lost with
the distillate water if the oil is not allowed to separate
completely. In addition, the temperature of the distillate may
have an important bearing on the efficiency of separation of
essential oil and water. The optimum temperature for obtaining
the best separation can be found by trial and error. Sometimes
when separation of oil is difficult, the distillate water is run
back into the still (cohobation) and redistilled.

Condensers and separators should
be constructed of materials which do not react with essential
oils or water. Mild steel rusts and is not suitable. However,
copper has been used successfully for many years tend tinned
copper were cooper reacts with the oil). The optimum material for
stills, condensers and separators is stainless steel which is
resistant and durable but is relatively expensive.

Most essential oils can be stored
for long periods under suitable conditions: they should be dry,
not in contact with the air or direct sunlight and kept cool.

It is important that essential
oils do not come into contact with materials with which they
might react, e.g. rubber or plastic bungs.

Glass containers are often used
for smaller amounts of oil but larger quantities are invariably
stored in metal drums. Mild steel drums lined with epoxy resin
are very popular for essential oils. If secondhand drums are to
be used, it is important that they are thoroughly cleaned and
dried before being filled with essential oil. Plastic containers,
e.g. polythene, should not be used because the oil may be
absorbed by the plastic and contamination may occur. To ensure
that the oil is not wet it should be left to stand for some time
before being filtered into its container. Oils generally show no
cloudiness when thoroughly dry.

Freshly distilled oils often
possess some "still odours" which are unpleasant. These
generally disappear after several weeks storage. Some oils
gradually improve in storage and acquire a fuller more rounded
aroma, e.g. vetiver and patchouli.

Cajuput, Cajuputi,
Kaju-Puti,Ti-Tree (not to be confused with Melalecua alternifolis
or Melalecua viridiflora)

CULTIVATION CONDITIONS

Occurs in natural stands and with
associated species in the Far East, principally Indonesia and the
Philippines. The tree grows to a height of 10 - 12 metres, but
only the shrub growth is used for the oil production. The oil is
produced all year round from the young leaves and terminal
branches (Guenther).

The young leaves yield
approximately 1% pale green to yellow oil. The oil has a powerful
fresh 'mildly medicated' odour. The taste is harsh and burning.

MAIN USES

For the inhabitants of South East
Asia this oil which has several names (Cajuput oil, Cajuputi oil,
Kaju-Puti oil, Ti-Tree oil, Cajaput oil), is a complete
all-purpose home medicine. The

Vietnamese hail the oil for its
antibacterial properties. Elsewhere it is widely used as an
expectorant, for throat preparations, such as gargles and for
stomach upsets. It is used in

Indonesia as an insecticide.
Total production is estimated to be between 75 and 200 tons
annually (Arctander).

It has not been fully considered
outside S.E. Asia. The smoothness of this cajuputol containing
oil, compared to the harshness of Eucalyptol oils for blending
with other flavours, has yet to be exploited.

II. AGRICULTURAL ASPECTS

CULTIVATION

Natural cultivation and
reforestation is sufficient for the present demand. It could be
readily cultivated in a plantation provided the usual precautions
are taken against tropical diseases and pests (Evans).

HARVESTING PERIOD

The leaves are collected all year
round.

HARVESTING METHODS

By hand, however plantations
could be harvested mechanically.

III. POST HARVEST TREATMENT, PRESERVATION, STORAGE

PRE-TREATMENT

There are no particular
requirements

PRESERVATION AND STORAGE

There are no particular
requirements

IV. PROCESSING

PROCESSING METHOD

By water/steam distillation in
mobile field stills. The stills are carried by two men on bamboo
poles. The spent leaf is used as the fuel. Modern equipment, in
particular the collecting system, would improve the yield, as the
oil does have some solubility in water.

Oil of Clausena anisata is a
mobile yellow clear liquid with a strong anise odour. On a dry
weight basis the yield is reported as 4.32% (Guenther).

MAIN USES

In Indonesia and the Philippines
the oil is used as a medicinal flavour and in the Philippino
local brandy "Anisdos". While the world interest in
this oil was wiped out with the availability of synthetic
anethole for aniseed, it has remained in use to save foreign
currency. In East Africa the dried leaves are used as an insect
repellent and the oil has been reported to be toxic to the
grasshopper "Zonecerus variegate" (Okunade).

II. AGRICULTURAL ASPECTS

CULTIVATION

The shrub can be propagated from
seed t Guenther) or more easily as grafts on Clausena excavate.

HARVESTING PERIOD

This has not been investigated
but is considered to be "as required".

HARVESTING METHODS

By hand, no commercial mechanical
harvesting is known.

III. POST HARVEST TREATMENT, PRESERVATION, STORAGE

PRE-TREATMENT

None specified

PRESERVATION AND STORAGE

The oil is susceptible to
oxidation and, therefore, should be stored in full, airtight
containers in a cool dark place.

IV. PROCESSING

PROCESSING METHOD

Water/steam or steam distillation
is satisfactory

COMPOSITION OF OIL

Nineteen components have been
identified in the leaves, with phenylpropanoids making up 96%,
methyl havicol (estragole) being the most abundant at 92%
(Ekundayo).

EQUIPMENT

Distillation retorts with heat
exchangers made from stainless steel

There is no identifiable
information for the following areas: PROCESSING oil extraction,
and nomenclature of products

Davana is an indigenous herb of
Southern India but does not grow wild to any great extent and is
cultivated mainly for the leaves and flowers used in Indian
garlands (Arctander). It is an annual, grown from seed and it
reaches maturity in four months.

MAJOR PRODUCING COUNTRIES

India (1 tonne)

YIELD AND DESCRIPTION

Yields have been reported ranging
from 0.13 - 0.58% with an average value of 0.2%. The oil is brown
in colour with a fine herbaceous sweet foliage odour which
becomes balsamic on drying. Because of the price it has caused
little interest outside the Indian sub continent.

The herb is susceptible to
nematodes (Haseeb).

MAIN USES

As a perfumery material.
Antifungal and antibacterial properties have been widely reported
for the oil (Alankara Rao, Alankara Rao).

II. AGRICULTURAL ASPECTS

CULTIVATION

The plants are readily cultivated
from seeds. These are planted in December and the seedlings are
planted out after 4 - 6 weeks. Artificial irrigation is used.
Davana farming has been very labour intensive, i.e. the
propagation, planting out, weed control and harvesting (Kumar).

HARVESTING PERIOD

This is usually 4 months after
planting and just prior to inflorescence. Artemisia pallens Wall.

HARVESTING METHODS

Reports indicate this has been by
hand (Gowda). The herb is dried for a week in the shade.

III. POST HARVEST TREATMENT, PRESERVATION, STORAGE

PRE-TREATMENT

Nematodes have to be combatted
(Arctander).

PRESERVATION

None required

STORAGE

In clean airtight drums

IV. PROCESSING

PROCESSING METHOD

Normal herbage distillation
techniques are used (Denny). The herb is dried, as above. The
spent herb can be used as fuel.

COMPOSITION OF OIL

The early reports were summarised
by Lawrence (Lawrence). More recently the ketone and furan have
been discussed with interest (Akhila). The main component is
davanone and this, and related compounds, have been used to
identify Davana Oil (Sandra).